The question to be addressed by this workship is whether or not there is any "natural" (biological) upper limit to the life expectancy of a human population in environments such as those provided by developed countries. An answer to this question depends upon the extent to which a biological foundation can be given to the demographic analysis or mortality. This workshop is designed to promote the necessary inter-disciplinary communication between theoretical and applied biologists (who do research on aging and death) and theoretical and applied demographers (who specialize in the study of human mortality). The proposed workshop is an outgrowth of an invited panel, organized for the May 1987 meetings of the Population Association of America, in which five speakers considered the problems related to estimating an upper limit to human life expectancy. Since no firm conclusions were reached, it was deemed appropriate to apply for funds to provide a more productive forum in which biologists and demographers could discuss in greater depth how a biological foundation could be given to the estimation of future trends in human longevity. The projected scale of the workshop is small. Twenty participants will be invited for a two-day period. Five discussion sessions have been scheduled, the purpose of which is to systematically integrate biological and demographic perspectives on the analysis of human mortality for purposes of estimating an upper limit to human life expectancy. The workshop format involves commissioning several papers, which will summarize the state of research invarious key areas. The ultimate goal is to publish a set of conceptually and empirically integrated papers (an edited treatise), with comments by those who attended the conference, on the biology of human mortality as it relates to estimating an upper limit to human longevity.